Over the last several decades, burgeoning offshore oil and gas well drilling and production industry have spawned the laying of subsea pipelines across the ocean floor. Typically, it is necessary for these subsea pipelines to be laid and serviced by divers. It is of course, as in all types of flow lines, necessary to install valves in the subsea pipelines in order to control flow for making repairs or for other purposes. Many of these subsea pipelines are fairly large in diameter and thus the valves are also extremely heavy and large in size and thus difficult to install. Like all valves, subsea valves occasionally malfunction and need repair. In known subsea valves, it is necessary for divers to remove the entire valve including the housing from the flow line in order to repair the valve. After removal, the valve can be raised to a ship deck and repaired and then replaced in the pipeline or a new valve can be put into the pipeline. In either event, it is necessary for the divers to remove the entire valve from the pipeline in order to make many types of repairs. Such removal is time consuming, difficult and expensive.